Copper base alloys

ABSTRACT

COPPER BASE ALLOYS CONTAINING AL, SI AND CO; AND AL, GE, CO ALLOY ADDITIONS IN THE TEMPER ROLLED OR TEMPER ROLLED AND ANNEALED CONDITIONS. THE ALLOYS OF THE PRESENT INVENTION ARE CHARACTERIZED BY EXCELLENT WORK HARDENING CHARACTERISTICS.

Sept. 26, 1972 RANE ETAL 3,694,273

COPPER BASE ALLOYS Original Filed June 14, 1968 a ZQ Cum: ALLOYS cu+zn ALLOYS 7 149+ Zn ALLOYS A +Az ALLOKS I 0 l I I 7-00 7-10 7-20 [-30 ELECTRON-ATOM RA T/O INVENTORS.

JACOB CRANE JAMES A. FORD ATTORNEY United States Patent Oflice Patented Sept. 26, 1972 3,694,273 COPPER BASE ALLOYS Jacob Crane, 230 Hill St., Hamden, Conn., and James A. Ford, 51 Pool Road, North Haven, Conn. 06473 Continuation of abandoned application Ser. No. 737,110, June 14, 1968. This application Dec. 21, 1970, Ser.

Int. Cl. C22c U.S. Cl. 148-32 4 Claims ABSTRACT OF THE DISCLOSURE Copper base alloys containing Al, Si and Co; and Al, Ge, Co alloy additions in the temper rolled or temper rolled and annealed conditions. The alloys of the present invention are characterized by excellent work hardening characteristics.

This application is a continuation of U.S. application Ser. No. 737,110 filed June 14, 1968, now abandoned.

Copper base alloys represent a large class of commercial metals finding a wide variety of uses. It is highly desirable to provide copper base alloys having high temper rolled strength and which also possess good ductility. Naturally, it is also desirable to provide such alloys which are economical, both from the standpoint of material cost and cost of manufacturing.

Typical commercial alloys having good temper rolled strength are marked by low ductility, e.g., elongation less than 2% at reductions of 50% or greater. In contrast, the alloys of the present invention have high temper rolled strength and provide improved ductility, e.g., elongation generally in excess of 3% for reductions of 50% or greater. Furthermore, the properties obtained by the alloys of the present invention are readily attainable by conventional copper base alloy processing, viz, casting, hot and cold rolling. The alloys of the present invention do not require special thermal processing designed to improve ductility, such as is required by the age hardening copper-beryllium alloys or the martensitic copper-aluminum alloys.

It is, therefore, a primary object of the present invention to provide a series of copper base alloys satisfying the above needs.

It is a further object of the present invention to provide novel copper base alloys having excellent work hardening behavior such that high yield and tensile strengths are obtainable accompanied by a high degree of ductility.

It is a still further object of the present invention to provide copper base alloys as aforesaid characterized by a relatively low cost and ease of manufacture.

Additional objects and advantages of the present invention will be more readily apparent from a consideration of the ensuing specification.

In accordance with the present invention, the foregoing objects and advantages are readily obtained and a novel series of copper base alloys are provided which have good work hardening characteristics.

The alloys of the present invention are characterized as follows: They contain at least one alloying element selected from Groups II, III and IV of the Periodic Table of Elements which will reduce the stacking fault energy of copper to below about 3 ergs per square centimeter, said alloying elements being present in substantially saturated solid solution in a copper matrix.

The alloys of the present invention attain numerous highly desirable advantages. They show excellent work hardening behavior such that high yield and tensile strengths are obtainable accompanied by high degree of ductility. They present high strength for a given elongation in the higher rolled tempers. They are readily hot rollable and cold rollable and present a relatively low fabrication cost.

In addition, the alloys of the present invention show an increase in cold rolled strength when given a low temperature thermal treatment.

The alloys of the present invention find wide use in those applications currently specifying high strength, temper rolled copper alloys, since they possess higher strength for a given elongation. For example, one can readily obtain an ultimate tensile strength of 100,000 p.s.i. along with a 3% elongation. In addition, the alloys of the present invention generally possess other desirable properties, such as good electrical conductivity. The desirable combination of high strength and good ductility in temper rolled material results in increased formability over that achieved with standard commercial alloys. The alloys of the present invention also exhibit good formability in the annealed condition. At the same time, their fabrication and material costs are less than or comparable to the most readily fabricated copper base alloys.

Other advantageous features of the alloys of the present invention will be apparent in the ensuing specification.

As indicated hereinabove, the copper base alloys of the present invention contain at least one alloying element which reduces the stacking fault energy of copper to below about 3 ergs per square centimeter. The stacking fault energy of copper is about 30 ergs per square centimeter. The most desirable alloying elements are those which cause the greatest reduction of stacking fault energy of copper and thereby facilitate fault formation.

Copper and a-copper solid solution alloys crystallize in the face centered cubic crystal structure. This crystal structure may deform by slip on close packed layers of atoms corresponding to the {111} planes. The slip deformation is accomplished by the motion of dislocations on these close packed 111} planes. The amount of slip accomplished by the motion of a dislocation is defined by the Burgers vector which in the face centered cubic structure is /2 a l10 It has been shown that this unit dislocation, /2 a 110 can dissociate into so-called half-dislocations resulting in a lower energy condition. Contained between these so-called half-dislocations will be a stacking fault.

The stacking fault may be best described and illustrated by considering how close packed {111} planes are arranged in the face centered cubic structure. These planes are stacked on one another in the sequence ABCACABC The arrangement of atoms on one of these close placked planes is shown in FIG. 1 which is taken from Dislocations And Plastic Flow In Crystals by A. H. Cottrell, page 73, 1st edition, 1953. Referring to FIG. 1, the B and C plane atom positions are given by the letters B and C. Described in FIG. 1 as Vector Arrows are the unit dislocations b and the respective half-dislocations b and b It can be seen that if the atoms are regarded as spheres it would be easier for slip to occur along the path defined by 11 and b than along the path defined by b If slip occurs along a Vector such as b between two of these close packed planes, i.e., if slip occurs by half-dislocation motion, a fault will be produced such that the stacking sequence becomes ...ABCACABC...

This stacking fault causes the structure to assume a ment of next nearest neighbor atoms in the face centered cubic structure has been changed.

Heidenriech and Shockley, Report on Strength of Solids (London: Physical Society), 57 (1948), have suggested that a unit dislocation in the face centered cubic structure would dissociate into two half-dislocations. For example, in the case of a unit dislocation on a {111} plane, the reaction would occur. This reaction results in a lower energy for the two half-dislocations with respect to the original unit dislocation. These half-dislocations, because of their elastic self-energies, will repel one another and produce a sheet of stacking fault in the slip plane between them. The extent of the half-dislocation separation will be defined by the increase in lattice energy associated with the stacking fault. Under equilibrium conditions the half-dislocations will be separated by a distance '7 which is defined by the following equation where ,u. is the shear modulus, a the lattice parameter, and e the fault energy.

Metallic elements each exhibit particular stacking fault energies. For example, aluminum exhibits a stacking fault energy of approximately 270 ergs per square centimeter and copper exhibits a stacking fault energy of 30 ergs per square centimeter. The addition of certain solutes, mainly those having appreciable solubility and vaIences higher than the solvent material, will reduce the stacking fault energy of the solute thus permitting large separation of the half-dislocations. The effect of several alloying additions to copper is shown in FIG. 2 which is taken from A. Howie and P. R. Swann, Phil. Mag." [8] 6, 1215 (1961). In FIG. 2, the electron to atom ratio is the ordinate and the stacking fault energy is the abscissa.

A further elaboration on these concepts may be found in The Direct Observation of Dislocations, by S. Amelincks, published by Academic Press Inc., 1964'.

When one ore more alloying element is utilized, and in the preferred embodiment two or more alloying elements are used, the combination of these alloying elements must reduce the stacking fault energy of copper to the required level. It is further preferred that the stacking fault energy be reduced as close to zero as possible.

The alloying elements must be present in substantially saturated solution in a copper matrix, i.e., the amounts of alloying elements must be such that copper is saturated with respect to the alloying elements. This insures that both the stacking fault energy will be a minimum and that the strength will be a maximum. An excess may be provided in order to insure saturation. The excess will be present as a precipitated secondary equilibrium phase. In accordance with the present invention, the excess secondary equilibrium phase must be present in an amount less than 20% by volume. In other words, the primary phase represents a saturated solid solution of the alloying element in copper and the secondary phase is a precipitate of the secondary equilibrium phase appropriate for the particular alloy system.

The alloying elements are selected from Groups H, III and IV of the Periodic Table of Elements. A preferred Group II element is zinc, preferred Group III elements are aluminum, gallium and indium and preferred Group IV elements are silicon and germanium. Preferred alloying elements are those which reduce the stacking fault energy most rapidly to a value of about 3 ergs per square centimeter or less. It has been found that the stacking fault energy is reduced in accordance with the electron to atom ratio of the solid solution and therefore high valence solute atoms are generally preferred. A further preference is given to those elements which have a high solubility in copper.

The amount of elements used will depend on their relative solubility in copper and their ability to lower the stacking fault energy of copper to the required level. As stated hereinbefore, the alloying element is provided in substantially saturated solid solution in copper.

Preferred systems utilize (1) aluminum and silicon as alloying elements with aluminum being present in an amount from 2.0 to 6.0%, optimally from 2.5 to 4.0% and silicon being present in an amount from 1.0 to 4.0% and optimally from 1.5 to 3.0% and (2) aluminum and germanium with aluminum as above and germanium from 3.0 to 5.0%.

In addition to the foregoing alloying elements, the alloys of the present invention preferably utilize at least one transition element, preferably iron, nickel, cobalt or zirconium, with the transition element being present in an amount from 0.01 to 5.0% by weight and preferably from 0.1 to 1.5% by weight. The transition elements retard grain growth at elevated temperatures and thereby increase annealed strength. In addition, they tend to stabilize temper rolled properties at given amounts of cold work and generally provide higher tensile strengths for a given elongation.

The alloys of the present invention may contain additional optional additives in order to achieve particularly desirable results. In addition, impurities may be present which are conventional to copper base alloy systems.

The alloys of the present invention and improvements resulting therefrom will be more readily apparent from a consideration of the following illustrative examples.

EXAMPLE I A copper base alloy was prepared by conventional DC casting, hot rolling, cold rolling and interannealing. The alloy had the following composition: aluminum, 3.1%; silicon, 2.1%; balance essentially copper. The alloy had an electron to atom ratio of about 1.3 and is also an all alpha phase alloy. The stacking fault energy of the alloy was below 3 ergs per square centimeter and the alloying additions were present in essentially a saturated solid solution in a copper matrix.

The alloy was processed in the following manner to yield the following properties:

(1) 30% cold rolled after 550 C., 1 hour anneal:

UTS, p.s.i. 102,000 0.2% offset yield strength, p.s.i. 78,000 Elongation, percent 12 (2) 50% cold rolled after 550 C., 1 hour anneal:

UTS, p.s.i. 120,000

0.2% offset yield strength, p.s.i. 100,000

Elongation, percent 4 (3) 70% cold rolled after 550 C., 1 hour anneal:

UTS, p.s.i. 128,000 0.2% offset yield strength, p.s.i. 112,000 Elongation, percent 3 EXAMPLE II (1) 30% cold rolled after 550 C., 1 hour anneal:

UTS, p.s.i 114,000 0.2% offset yield strength, p.s.i. 89,000 Elongation, percent 5 (2) 50% cold rolled after 550 C., 1 hour anneal:

UTS, p.s.i 128,000 0.2% offset yield strength, p.s.i. 104,000 Elongation, percent 3 (3) 70% cold rolled after 550 C., 1 hour anneal:

UTS, p.s.i 134,000 0.2% offset yield strength, p.s.i. 111,000 Elongation, percent 3 EXAMPLE III 50% cold rolled after 600 C., 1 hour anneal:

UTS, p.s.i 110,000 0.2% offset yield strength, p.s.i. 90,000 Elongation, percent 5 This invention may be embodied in other forms or carried out in other ways without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered as in all respects illustrative and not restrictive, the scope of the invention being indicated by the appended claims, and all changes which come within the meaning and range of equivalency are intended to be embraced therein.

What is claimed is:

1. A copper base alloy in the temper rolled condition having good work hardening characteristics consisting of: two alloying elements which in combination reduce the stacking fault energy of copper to below 3 ergs per square centimeter selected from the group consisting of (A) aluminum from 2.0 to 6.0% plus silicon from 1.5 to 3.0% and (B) aluminum from 2.0 to 6.0% plus germanium from 3.0 to 5.0%, said alloying elements being present in substantially alpha saturated solid solution in a copper matrix; from 0.01 to 5.0% cobalt; and balance copper.

2. An alloy according to claim 1 in the temper rolled and annealed condition.

3. An alloy according to claim 1 consisting of aluminum from 2.0 to 6.0%, silicon from 1.5 to 3.0%, cobalt from 0.01 to 5.0%, balance copper.

4. An alloy according to claim 3 consisting of aluminum from 2.5 to 4.0%, silicon from 1.5 to 3.0%, cobalt from 0.1 to 1.5%, balance copper.

References Cited UNITED STATES PATENTS 1,838,632 12/1931 'Pacz -160 2,130,737 9/1938 Hensel et al. 75-159 2,048,549 7/ 1936 Harrington 75-162 X 2,270,716 1/ 1942 Morris 75160 2,870,051 1/1959 Klement 148160 3,259,491 7/ 1966 Pryor 75162 3,475,227 10/1969 Caule et al. 148--31.5 X

CHARLES N. LOVELL, Primary Examiner US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE CORRECTION Patent No. 3,694,273 Dated September 1 lnv nt fl Jacob Crane and James A'. Ford It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In Column 1, in the heading, line 4, after "Conn. 06473" insert assignors to Olin Mathieson Ch w emical a corporation of Virginia corporatlon,

. In Column 2, line 50, BCACABG-. should read ,ABCABCABC. I

In Column 2, line 51, the'word. "pla ckedf' should read ---packed---.

In Column 3, line 3, the word "Heidenriech" should read ---Heidenreich---; T

In Column 3, l'ine 1 o, "i/za[ g'il-n/edg'i'ilfl/eaffiz1 should read ---"1/2a[1o1]- 1/6a[211]+1/6a[112]---.

In Column 3, line 42, j the word "ore" should read Signed and sealed this 22nd day of May 1975.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBEI'iT GOTTSCHALK Attesting Officer T Commissioner of Patents 

